diff --git a/BuildSourceImage.sh b/BuildSourceImage.sh
index d0db1ca..ddee851 100755
--- a/BuildSourceImage.sh
+++ b/BuildSourceImage.sh
@@ -28,6 +28,10 @@ _usage() {
     echo -e "       -D\t\tdebuging output. Can be set via DEBUG env variable"
     echo -e "       -h\t\tthis usage information"
     echo -e "       -v\t\tversion"
+    echo -e ""
+    echo -e "    Subcommands:"
+    echo -e "       unpack\tUnpack an OCI layout to a rootfs directory"
+    echo -e ""
 }
 
 # sanity checks on startup
@@ -44,6 +48,23 @@ _init() {
     done
 }
 
+# enable access to some of functions as subcommands!
+_subcommand() {
+    local command="${1}"
+    local ret
+
+    shift
+
+    case "${command}" in
+        unpack)
+            # (vb) i'd prefer this subcommand directly match the function name, but it isn't as pretty.
+            unpack_img "${@}"
+            ret=$?
+            exit "${ret}"
+            ;;
+    esac
+}
+
 # _is_sourced tests whether this script is being source, or executed directly
 _is_sourced() {
     # https://unix.stackexchange.com/a/215279
@@ -292,6 +313,20 @@ unpack_img() {
     local unpack_dir="${2}"
     local ret
 
+    while getopts ":h" opts; do
+        case "${opts}" in
+            *)
+                echo "$0 unpack <oci layout path> <unpack path>"
+                return 1
+                ;;
+        esac
+    done
+    shift $((OPTIND-1))
+
+    if [ -z "${image_dir}" ] || [ -z "${unpack_dir}" ] ; then
+        _error "[unpack_img] blank arguments provided"
+    fi
+
     if [ -d "${unpack_dir}" ] ; then
         _rm_rf "${unpack_dir}"
     fi
@@ -336,9 +371,10 @@ unpack_img_bash() {
         return ${ret}
     fi
 
-    # Since we're landing the reference as an OCI layout, this mediaType is fairly predictable
-    # TODO don't always assume +gzip
-    layer_dgsts="$(jq '.layers[] | select(.mediaType == "application/vnd.oci.image.layer.v1.tar+gzip") | .digest' "${image_dir}"/blobs/"${mnfst_dgst/:/\/}" | tr -d \")"
+    # TODO this will need to be refactored when we start seeing +zstd layers.
+    # Then it will be better to no just get a list of digests, but maybe to
+    # iterate on each descriptor independently?
+    layer_dgsts="$(jq '.layers | map(select(.mediaType == "application/vnd.oci.image.layer.v1.tar+gzip"),select(.mediaType == "application/vnd.oci.image.layer.v1.tar"),select(.mediaType == "application/vnd.docker.image.rootfs.diff.tar.gzip")) | .[] | .digest' "${image_dir}"/blobs/"${mnfst_dgst/:/\/}" | tr -d \")"
     ret=$?
     if [ ${ret} -ne 0 ] ; then
         return ${ret}
@@ -1026,8 +1062,9 @@ main() {
     local work_dir
 
     _init "${@}"
+    _subcommand "${@}"
 
-    base_dir="$(pwd)/${ABV_NAME}"
+    base_dir="${BASE_DIR:-$(pwd)/${ABV_NAME}}"
     # using the bash builtin to parse
     while getopts ":hlvDi:c:s:e:o:b:d:p:" opts; do
         case "${opts}" in
diff --git a/Dockerfile b/Dockerfile
index 0714352..8c64206 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,4 +4,6 @@ RUN dnf install -y jq skopeo findutils file 'dnf-command(download)'
 
 COPY ./BuildSourceImage.sh /usr/local/bin/BuildSourceImage.sh
 
-ENTRYPOINT ["/usr/local/bin/BuildSourceImage.sh", "-b", "/tmp/"]
+ENV BASE_DIR=/tmp
+
+ENTRYPOINT ["/usr/local/bin/BuildSourceImage.sh"]
diff --git a/test/02-from_image_ref.bats b/test/02-from_image_ref.bats
index 74595d2..b9f1ce3 100644
--- a/test/02-from_image_ref.bats
+++ b/test/02-from_image_ref.bats
@@ -3,6 +3,7 @@
 load helpers
 
 @test "Build from image reference" {
+	#skip "this takes like 20min ..."
     local d
     d=$(mktemp -d)
     echo "temporary directory: ${d}"
diff --git a/test/03-unpack.bats b/test/03-unpack.bats
new file mode 100644
index 0000000..ee540cf
--- /dev/null
+++ b/test/03-unpack.bats
@@ -0,0 +1,32 @@
+#!/usr/bin/env bats -t
+
+load helpers
+
+@test "unpack - no args" {
+	run_ctr $CTR_IMAGE unpack
+	[ "$status" -eq 1 ]
+	[[ ${lines[0]} =~ "[SrcImg][ERROR] [unpack_img] blank arguments provided" ]]
+}
+
+@test "unpack - Help" {
+	run_ctr $CTR_IMAGE unpack -h
+	[ "$status" -eq 1 ]
+	[[ ${lines[0]} =~ "BuildSourceImage.sh unpack <oci layout path> <unpack path>" ]]
+}
+
+@test "unpack - from a SRPM build" {
+	local d
+	local r
+
+	d=$(mktemp -d)
+	echo "temporary directories: output - ${d}"
+	run_ctr -v $(pwd)/.testprep/srpms/:/src:ro --mount type=bind,source=${d},destination=/output $CTR_IMAGE -s /src -o /output
+	[ "$status" -eq 0 ]
+	[ -f "${d}/index.json" ]
+
+	r=$(mktemp -d)
+	echo "temporary directories: unpacked - ${r}"
+	run_ctr --mount type=bind,source=${d},destination=/output -v ${r}:/unpacked/ $CTR_IMAGE unpack /output/ /unpacked/
+	[ "$(find ${r} -type f | wc -l)" -eq 3 ] # regular files
+	[ "$(find ${r} -type l | wc -l)" -eq 3 ] # and symlinks
+}
diff --git a/test/helpers.bash b/test/helpers.bash
index 67428d9..8dbb1c1 100644
--- a/test/helpers.bash
+++ b/test/helpers.bash
@@ -1,3 +1,8 @@
+#!/bin/bash
+
+export CTR_IMAGE="${CTR_IMAGE:-localhost/containers/buildsourceimage}"
+export CTR_ENGINE="${CTR_ENGINE:-podman}"
+
 function run_ctr() {
 	run $CTR_ENGINE run --security-opt label=disable --rm "$@"
 }